The present invention relates generally to communication networks, and more specifically, to a technique for setting up pseudowire based circuits over a bridged network.
Pseudowire technology is currently used to create virtual wires which can be used for VPLS and frame relay transport over an IP or MPLS network. Pseudo Wire Emulation Edge-to-Edge (PWE3) emulates the essential attributes of a telecommunication service over a PSN (packet switched network). PWE3 provides only the minimum necessary functionality to emulate the wire with the required degree of accuracy for a given service. Pseudowire technology operates to encapsulate service-specific bit-streams, cells or PDUs (protocol data units) arriving at an ingress port, and carry them across an IP path or MPLS tunnel. Pseudowire may also be used to perform other operations such as managing timing and order to emulate the behavior and characteristics of the service to the required degree of accuracy. From the perspective of customer edge equipment, the pseudowire is an unshared link or circuit of the service.
Conventional use of pseudowire based circuits includes MPLS or L2TPV3 and techniques such as MAC in MAC, which is an alternative tunneling technology. Methods for transporting layer 2 packets over high-performance networks are described, for example, by Martini et al., in “Encapsulation Methods for Transport of Ethernet Frames Over IP/MPLS Networks” (IETF draft-ietf-ethernet-encap-00.txt, August, 2002), which is incorporated herein by reference. The term “layer 2” refers to the second layer in the protocol stack defined by the Open Systems Interface (OSI) model, also known as the logical link, data link, or MAC layer. This draft defines methods for encapsulating Ethernet traffic for transportation over IP networks using MPLS or other tunneling methods, such as Generic Routing Encapsulation (GRE). Ethernet LANs are connected to the IP network by provider edge devices, which are linked together by tunnels through the IP network. The sending provider edge device receives Ethernet frames from a customer edge device on the source LAN. It encapsulates the frames in packets with the label stack required for transmitting packets through the appropriate tunnel to the receiving provider edge device.
L2TPV3, described by Townsley et al in “Layer Two Tunneling Protocol (Version 3) ‘L2TPv3’” (IETF draft-ietf-12tpext-12tp-base-04.txt, November, 2002), which is incorporated herein by reference, is another technique for tunneling layer-2 packets over IP networks, which can be used to carry Ethernet packets within a provider network.
A drawback to these conventional pseudowire techniques using MPLS or L2TPV3 is that they require the use of a layer 3/IP network for setting up pseudowire circuits, thus there are no provisions for establishing pseudowire circuits over a pure layer 2 bridged network. A drawback for MAC in MAC is that it can only be used for Ethernet devices and requires Ethernet frame formats. These are significant constraints in cases where a layer 3/IP network or Ethernet frames cannot be used and yet the advantages of pseudowire technology are desired.
There is, therefore, a need for a system and method for using pseudowire technology without requiring the use of a layer 3/IP network for setting up the pseudowire circuits. It is also desirable that the system and method work for multiple types of clients and do not require new Ethernet frame formats.